Functions and Requirements of Spindles

The spindle of a machine tool is so designed so as perform the following important funtions:

 

The operational capabilities of machine tools in terms of productivity, accuracy, finish machine parts largely depend upon the extent to ehich the above functions are qualitatively satisfied. They also determine the important design requirements to spindle units which aregiven below:


 

Requirements
The spindle should rotate with high degree of accuracy. The accuracy of rotation is determined by the axial and radial run out of the spindle nose and these must not exceed certain permissible values which are specified depending upon the required machining accuracy. The rotational accuracy is influenced at the most by the stillness and accuracy of the spindle bearings, particularly the one located at the front end.

The spindle unit must have high static stiffness. The stiffness of the unit is made up of the stiffness of the spindle unit proper and the spindle bearings. Machining accuracy is influenced on bending, axial as well as torsional stiffness.

The spindle unit must have high dynamic stiffness and damping. Poor dynamic stability of the spindle unit adversely affects the dynamic behavior of the machine tool as a whole.